A road train consists of a lead vehicle driven by a professional driver followed by a number of self-driving vehicles. Building on Volvo’s existing safety systems (features such as cameras, radar and laser sensors) the vehicles monitor the lead vehicle and also other vehicles in their immediate vicinity. WIRELESS 'REMOTE' CONTROL

The addition of wireless communication allows the vehicles in the platoon to accelerate, brake and turn in exactly the same way as the leader, using autonomous control.

One lead vehicle and four trailing vehicles - Volvo S60, a Volvo V60 and a Volvo XC60 plus a truck - made up the historic road train in Spain.

Linda Wahlström, project manager for the SARTRE project at Volvo Car, said: "We covered 200 kilometres in one day and the test turned out well. We're really delighted. Driving among other road-users is a great milestone in our project.”

The vehicles drove at 85 kilometres an hour with the gap between each vehicle just six metres.

The Sartre project was designed to make drivers who spend most of their time in peak-hour, bumper-to-bumper traffic more comfortable and, because the vehicles run autonomously, drivers can use the time to read, work or eat. MORE THAN TIME-SAVING

As a bonus, the project also improves traffic safety, reduces the environmental impact by maintaining a steady speed and reduces the likelihood of traffic tailbacks.

The three-year Sartre project has been under way since 2009 and in testing, vehicles have covered about 10 000km. After the test on the public roads in Spain, the project is now entering a new phase with the focus on analysis of fuel consumption.

"We've learnt a whole lot during this period. People think that autonomous driving is science fiction, but the fact is that the technology is already here. From a purely conceptual viewpoint, it works fine and road trains will be around in one form or another in the future," Wahlström concluded.

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